Conventionally, a liquid sample analyzer, especially, a device for analyzing a biological sample such as blood comprises a nozzle that is inserted into a sample container as a closed container and a suction mechanism such as a syringe to suck a liquid sample such as blood from the nozzle. The nozzle and the suction mechanism are connected by an elastic tube having elasticity.
However, in case that a pressure in the sample container is bigger than a pressure (atmospheric pressure) in the elastic tube, when the nozzle is inserted into the sample container, there is no space left for the pressure in the sample container and the pressure in the nozzle to escape because the sample container and the elastic tube are in a tightly closed state. As a result, the pressure in the elastic tube rises and becomes in a pressurized state during a process while the pressure in the sample container and the pressure in the elastic tube change to an equilibrium state. At this time, the elastic tube fails to keep its volume constant against the pressure and inflates. Then the blood enters the nozzle by an amount that the elastic tube inflates. Once the blood enters the nozzle, a slight amount of the blood attaches an inner wall of the nozzle and remains in the nozzle, even though the pressure in the sample container later becomes the atmospheric pressure.
In addition, in case that the flow channel in the nozzle, the elastic tube and the syringe are filled with a liquid such as a diluted solution, when the blood enters the nozzle, the blood is mixed with the liquid so that the blood still remains in the nozzle.
As mentioned, in case that the quantitative determination is conducted based on a volume of a flow channel in the nozzle and a volume of a flow channel in the elastic tube, there is a problem that it fails to conduct an accurate quantitative determination. Meanwhile, in case that the pressure in the sample container is smaller than the atmospheric pressure, an adverse phenomenon occurs. Then in case that the nozzle is filled with a liquid such as a diluted solution, the liquid flows into the closed container from the nozzle and the blood is diluted by the liquid, resulting in failing the accurate quantitative determination.
In order to solve these problems, as shown in the patent document 1, there is an arrangement wherein a means to open the closed container to the atmosphere is arranged in the nozzle.
However, with this arrangement, it fails to deal with a rapid pressure change at a moment when the nozzle is inserted into the closed container or at a time when the nozzle is pulled out from the closed container so that there is still the above-mentioned problem. Patent document 1: Japan patent laid-open number 2004-170156